Optimal transport and anomalous thermal relaxations

TL;DR

This paper explores the relationship between optimal transport theory and anomalous thermal relaxation phenomena like the Mpemba effect, revealing conditions under which they coincide or differ in continuous and discrete systems.

Contribution

It establishes a connection between optimal transport and the Mpemba effect, showing that in discrete systems they can occur simultaneously under certain dynamics.

Findings

In continuous systems, the Mpemba effect is linked to high entropy production.

In discrete systems, optimal transport can coincide with the Mpemba effect for specific protocols.

The study highlights differences between continuum and discrete models in thermal relaxation behaviors.

Abstract

We study connections between optimal transport and anomalous thermal relaxations. A prime example of anomalous thermal relaxations is the Mpemba effect, which occurs when a hot system overtakes an identical warm system and cools down faster. Conversely, optimal transport is a resource-efficient way to transport the source distribution to a target distribution in a finite time. By "a resource-efficient way," what is often meant is with the least amount of entropy production. Our paradigm for a continuum system is a particle diffusing on a potential landscape, while for a discrete system, we use a three-state Markov jump process. In the continuous case, the Mpemba effect is generically associated with high entropy production. As such, at large yet finite times, the system evolution toward the target is not optimal in this respect. However, in the discrete case, we show that for specific dynamics, the optimal transport and the strong variant of the Mpemba effect can occur for the same relaxation protocol.